#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
int main1()
{
	char arr[] = "I Love You";
	int sz = sizeof(arr) / sizeof(arr[0]);
	int i = 0; 
	for (i = 0; i <=sz; i++)
	{
		if (arr[i] >= 'A' && arr[i] <= 'Z')
		{
			arr[i] += 32;
		}

	}
	printf("%s ", arr);

	return 0; 
}
#include <ctype.h>
int main2()
{
	char arr[] = "I Love You";
	int sz = sizeof(arr) / sizeof(arr[0]);
	int i = 0; 
	while (arr[i] != '\0')
	{
		if (islower(arr[i]))
		{
			arr[i] -= 32;
		}
		i++;
	}
	printf("%s", arr);

	return 0; 
}
int main3()
{
	char c = toupper('e');//小写转大写
	printf("%c\n", c);
	char a = tolower('E');//大写转小写
	printf("%c\n", c);

	return 0; 
  }

//strlen 实现

int Strlen(char  *arr)
{
	int count = 0;
	int i = 0;
	while (*arr != '\0')
	{
		count++;

		arr++;
	}

	return count ;

  }
int main()
{
	char arr[] = "Lzfxx";
	 size_t r =Strlen(arr);
	 printf("%zd ", r);
	return 0;
}